1. Field of the Invention
This invention relates to a two-half type mechanical seal device comprising two halves each having a splitting face extending axially that are combined from the radial direction of a rotational shaft to couple together, and more particularly to a two-half type mechanical seal device constituted as an outside seal device for sealing a high pressure fluid.
2. Description of the Related Art
As a first related art relating to the invention there exists a mechanical seal device, as shown in FIG. 3.
FIG. 3 is a sectional view, showing the upper half of a mechanical seal device 100 according to the first related art. The mechanical seal device 100 is an inside seal device. A rotational shaft 148 passes through a passage 151 in the housing 150 to which the mechanical seal device 100 is mounted. To the end face of the housing 150 is secured a gland assembly 140 with screw bolts (not shown) through a gasket. The gland assembly 140 is also comprised of two halves that are split along the axial plane. In the gland assembly 140, those two halves are joined together at their mating faces with a plurality of screw bolts (not shown).
A mechanical seal is disposed inside of the inner face 141 of the gland assembly 140. Tis mechanical seal is provided with a holder assembly 102 that is also comprised of two halves and mounted on the rotational shaft 148 for rotation therewith. The two halves of the holder assembly 102 are joined together at their splitting faces with a plurality of screw bolts. Between the outer face of the holder assembly 102 and the inner face 141 of the gland assembly 140 is formed a fluid passage 142 through which the sealed fluid flows. Further, a first O-ring 131 for sealing the fitting section between the rotational shaft 148 and the holder assembly 102 is fitted in an annular groove 105 formed in the inner face of the holder assembly 102.
At one end face of the holder assembly 102 is formed a recess 146 having a bottom surface to which one or more drive pins 135 are fixed and having a step section 145 on which an O-ring is seated.
Within the recess 146 of the holder assembly 102 is installed a rotational seal ring 101 that is also comprised of two halves that are split in the axial direction. The rotational seal ring 101 has a rotational sealing face 106 at one end and one or more engagement sinks 103 at the other end for the engagement with the corresponding drive pins 135. Between the step section 145 of the holder assembly 102 and the outer face of the rotational seal ring 101 is provided a space 133 in which a second O-ring 132 is disposed. The second O-ring 132 is adapted to fasten the splitting faces to closely contact the two halves of the rotational seal ring 101 and adapted to seal the space 133. An inlet 144 is also formed to allow the sealed fluid to enter the space 133.
An axial two-half type stationary seal ring 110 having a stationary sealing face 111 in close contact with the rotational sealing face 106 is fitted to the rotational shaft 148 with a gap therebetween. The stationary seal ring 110 is disposed within the space defined by the inner space defining face 143 of the gland assembly 140 and is movably fitted to a fitting surface S. The stationary seal ring 110 is biased toward the rotational seal ring 102 by a plurality of leaf springs 130 mounted at the end of the gland assembly 140. Further, a space chamber 114 is formed between the outer face of the stationary seal ring 110 and the inner space defining face 143. A third O-ring 137 is provided in the space chamber 114. The third O-ring 137 is adapted to fasten the mating surfaces to closely contact the two halves of the stationary seal ring 110 and adapted to seal the space chamber 114.
In the mechanical seal device 100 of the first related art constituted in such a way described, it is required to provide the two-half type gland assembly 140 in which a mechanical seal is build. The gland assembly 140 necessarily has a complicated structure due to its two-half constitution in which the two halves are assembled with screw bolts and due to the attachment of the gland assembly 140 to the end face of the housing 150 with screw bolts. Accordingly, there is a problem that the gland assembly 140 becomes larger in size. Also, the two-half type holder assembly 102 assembled with screw bolts has a complicated structure and a large size because it contains the rotational seal ring 101. The large size of the holder assembly 102 makes the mechanical seal device larger in its overall size. The higher the pressure of the fluid to be sealed is, the larger the thickness required for the components of the gland assembly 140 becomes, causing the entire structure to be large in size.
A plurality of leaf springs 130 circumferentially located at the end of the gland assembly 140 make the structure further complicated. There is also a problem that it becomes more difficult to fabricate the entire seal device because of the increase of the total number of parts.
Further, when the pressure of the sealed fluid is high, the high pressure fluid from the fluid passage 142 acts on the second O-ring 132 and the third O-ring 137. This causes the deformable seal rings 101 and 110 of silicon carbide or carbon of the split structure to be easily deformed by the pressure of the sealed fluid and as a result, the sealing faces 106 and 111, specifically the rotational sealing face 106 is deformed, which leads the sealed fluid to leak between the sealing faces 106 and 111.
Further, there exists a two-half type, outside mechanical seal device 200 as a second related art, as shown in FIG. 4.
In FIG. 4, the two-half mechanical seal device 200 is provided for sealing the sealed fluid between a rotational shaft 148 and a housing 150 through which the rotational shaft 148 passes. The fluid is sealed by a stationary sealing face 161 through the inner face side of a stationary seal ring 160.
The axial two-half type stationary seal ring 160 for sealing the fluid on its inner face side has an inner face fitted to the rotational shaft 148 with a gap therebetween. This gap formed between the inner face of the stationary seal ring 160 and the outer face of the rotational shaft 148 defines a fluid passage for the sealed fluid.
The stationary seal ring 160 has an outer face fitting to the inner face 167 on one side of an annular gasket 165 comprised of combined two thick halves each having the L shaped sectional area. The end face 166 on the other side of the gasket 165 is in close contact with the end face of the housing 150. The gasket 165 is also split into two halves. Those two halves can be in close contact with each other in a way that projections and recesses formed on the splitting faces of two halves are closely fitted to each other.
The stationary seal ring 160 is secured through the gasket 165 to the inner face 167 on one side of an axial two-half type stationary holder 168, the other end of which is fitted and secured to the projection formed in one end of the housing 150. In order to assemble the stationary two-half type holder 168, two halves of the two-half stationary holder 168 are fastened with two screw bolts 153 and coupled together.
In the two-half stationary holder 168, in order to compensate for holding the stationary seal ring 160 fittingly secured on other side while one end is fittingly secured to the projection of the housing 150, one of the fitting sections has a recess or undercut. In this recess structure, the part of the gasket 165 sandwiched by the two-half holder 168 and the stationary seal ring 160 is made thick.
The two-half type rotational seal ring 170 is fitted to the rotational shaft 148 with a gap therebetween and has at one end a rotational sealing face 171 in close contact with the stationary sealing face 161 to seal the fluid. The outer face of the rotational seal ring 170 is fitted to the inner face 177 of a second gasket 175 and secured through the gasket 175 to a two-half type rotational holder 178. The gasket 175 is also split into two halves. Those two halves engage with each other in a way that projections and recesses formed on the splitting faces of two halves are fitted to each other.
The two-half type rotational holder 178 is comprised of two halves split in the axial direction and couples to the rotational shaft 148 through a key. The two halves are fastened by two screw bolts 154 and envelope the rotational shaft 148 and the rotational seal ring 170. Accordingly, as has been described, between the rotational seal ring 170 and the two-half rotational holder 178, one end of the thick gasket 175 supports them elastically. The other end of the gasket has the inner face 176 fitted to the rotational shaft 148 and pressed against the rotational shaft 148 and the two-half rotational holder 178 for sealing therebetween.
In the mechanical seal device 200 as a second related art constituted as has been described, when the two-half stationary holder 168 is mounted, two fitting sections must be fitted at the same time. It is therefore required to provide a thick gasket for one of the two fitting sections, that is, at the fitting section at the stationary seal ring 160. Similarly, the gasket 175 has a thick portion between the two-half rotational holder 178 and the rotational seal ring 170.
Accordingly, if the sealed fluid has a high pressure, then the gaskets 165 and 175 are pressed to contact in the radial direction. This causes the mating faces of the two-half type stationary seal ring 160 to be separated and, as a result, the fluid to be sealed will leak outside.
Furthermore, since the gaskets 165 and 175 are deformed due to the pressure of the sealed fluid, the sealing faces 161 and 171 are forced to incline in opposite directions to each other and, as a result, also the fluid to be sealed will leak.
Additionally, although the two-half type stationary and rotational holders 168 and 178 are simplified in the drawing, they have a complicated structure and are difficult to be fabricated, because both must be fitted to the housing 150, the rotational shaft 148 and seal rings 160 and 170, respectively, through the gaskets 165 and 175. Therefore, the cost will be reduced.
The present invention is made in view of the problems described above, and the technical problem to be solved by the invention is to provide a mechanical seal device having a simplified structure and the reduced number of parts or components, as well as cost reduction.
Another technical problem is to provide a mechanical seal device adapted to apply without reduction of sealing ability in the wide range from high to low pressure of the sealed fluid.
Another yet technical problem is to provide a mechanical seal deice for sealing the sealed fluid of high viscosity or high content of slurries, as well as chemical liquid, without any problems with the sealing ability.
The present invention is made for solving the technical problems described and the technical means for solving the problems are constituted as follows.
The mechanical seal device of a preferred first embodiment according to the invention is a mechanical seal device of outside seal type for sealing the fluid to be sealed between a rotational shaft and a housing through which the rotational shaft passes, comprising: a two-half type stationary seal ring having a first sealing face at one end and retained fluid-tightly by the housing so as to be movable axially; a first two-half type fastening ring fitting to the outer face of the two-half type stationary seal ring and closely contacting the split contact faces of the two-half type stationary seal ring, the first two-half type fastening ring having splitting faces adapted to be engaged and disengaged with each other; a two-half type rotational seal ring having a second sealing face in close contact with the first sealing face and having axially split contact faces, the two-half type rotational seal ring coupling fluid-tightly with the rotational shaft for rotation therewith; and a second two-half type fastening ring fitting to the outer face of the two-half type rotational seal ring and closely contacting the split contact faces of the two-half type rotational seal ring, the second two-half type fastening ring having splitting faces adapted to be engaged and disengaged with each other, wherein a gap through which the sealed fluid passes is defined between the inner face of the two-half type stationary seal ring and the rotational shaft, and wherein the two-half type stationary seal ring is elastically biased against the two-half type rotational seal ring by a biasing means.
In the mechanical seal device of the invention relating to the first embodiment, the two-half type stationary seal ring is so called an outside seal in which the sealed fluid pressure originates on the inner face side and acts outwardly. Furthermore, this mechanical seal device has such a structure that the outer face is secured directly by the two-half type fastening ring or the housing. Therefore, the splitting faces are not forced to be separated to open. Therefore, the fluid of high to low pressure can be sealed.
Also, since the two-half type stationary seal ring has a single component constitution fitting to the two-half type fastening ring for retaining the outer face of the former, the number of parts is minimized, resulting in cost reduction.
Additionally, since the two-half type stationary seal ring has a simplified structure, there is no section to which high viscosity fluid, high slurry contained fluid or chemical liquid as the sealed fluid sticks. This allows the sealing ability to be effectively maintained.